GMAT考题：OG2017Q-DS-195

GMAT考题

For all x, the expression x* is defined to be ax + a, where a is a constant. What is the value of 2* ?

(1) 3* = 2

(2) 5* = 3

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

EACH statement ALONE is sufficient.

Statements (1) and (2) TOGETHER are NOT sufficient.

毕出

题目分析：

x*=ax+a，由于未知量a的存在，需要求得a方能算出x*，所以2*=2a+a=3a

（1）3*=3a+a=4a=2，a=0.5，所以有2*=3a=1.5。题目得解。

（2）5*=5a+a=6a=3，a=0.5，所以有2*=3a=1.5。题目得解。

因此，本题答案为（D），任何一个条件说明均能解题。

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